Abstract

Embryos production allows increasing the genetic progress as well as conserving and exchanging genetic material. Nowadays production protocols based in the use of six to eight FSH crescent doses are used. This fact determines a frequent manipulation of the animals, which not only increases the costs, but also it is more difficult to carry it out in commercial farms located away from the transference centres. The objective of this research was to reduce the FSH application to one single dose. Forty-seven female, heterozygotes (FecB Fec+) Corriedale Booroola, were tested. Seven treatments were evaluated by combining different FSH doses and administration scheduling. Estro synchronization was similar in all the treatments: fourteen days of medroxiprogesterone intravaginal pessaries and the administration of 200 IU of eCG once the pessaries were retired and the administration of GnRH thirty five hours later. The treatments were T1 (Traditional Protocol), T2 and T3 were based in the administration of FSH doses of 156, 124 y 46 mg (eight decreasing doses). The treatments based in a single FSH dose (124 mg) varied in the moment of its application: 36 h, 24 h, 12 h before, and simultaneously with the pessaries extraction (0 h). The described treatments are T4, T5, T6 and T7. The obtained ovulatory rate was 10.9; 12.5; 5.0; 0; 8.9; 6.3 and 8.3 for the seven treatments respectively. The smaller rate corresponded to T3 (P<0.05) and null (without ovulation) in T4. The amount of free able embryos by treatment was 4.0; 5.0; 3.3; 0; 2.9; 4.5 and 1.7. The results shown that lower doses than those used in the Traditional Treatment gave the same amount of embryos (T1 vs T2). Likewise, a single FSH dose applied in Corriedale Booroola ewes (T6) allows producing a similar amount of good quality embryos.

Keywords: Multiovulation; FSH; Embryo production; Booroola

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